Pressure relief devices



United States Patent 11113543367 [72] Inventors Hans Theodor Grisebaeh[56] R f c s Cit d fi 1 UNITED STATES PATENTS 21 A I N a?! 1,603,51410/1926 Carter 137/494 l 3 2,005,813 6/1935 Thorsen 137/538)( [22] FiledMay 13,1969 2 033 839 3/1936 L awson l37/538X [45] 2 825 309 3/1958 Geier 137/494x [731 (mum wand 3 482 594 12/1969 Simin 137/538 WethmunmLune, westfaua, Ge y a body corporate of Germany Primary Examiner-M.Cary Nelson [32] Priority June 10, 1968 Assistant Examiner-Robert J.Miller [33] Germany Attorney-Sughrue, Rothwell, Mion, Zinn & Macpeak(31] No. 1,750,834

ABSTRACT: A pressure-relief device in the form of a piston slidablymounted in a bore of a housing, an o-ring being provided between thebore and the piston. The piston has a longitudinal bore extendingcompletely through the piston which [54] gz g gk fg g bore communicateswith radial bores which can be moved inwardly beyond the O-ring againstthe force of a spring to per- [52] US. 137/494, mit a through flow ofpressure fluid. The inner most end of the 137/5122, l37/5l2.5, 137/538longitudinal bore is normally closed by a pressure member [5 1] Int.F16: 17/04 transmitting the spring force to the piston, the pressure[50] Field ofSearch 137/494, member being separable from the piston.When the pressure (inquired), 535, 538; 512.2, 512.5, 512

within the longitudinal bore reaches a certain value.

BACKGROUND OF THE INVENTION Pressure relief devices are known forexample in mineral mining. A known device which has been used quiteextensively is composed of a housing provide d withina bore containing apiston the outer working face of which is exposed to pressure fluid tobe controlled. The piston has alongitudinal bore extending inwardly fromits working face to communicate with a number of radial bores, extendingto the peripheral surface of the piston. When the pressure acting on theworking face of the piston exceeds a certain value the piston isdisplaced into thehousing against the force ofa spring until the radialbores are positioned inwardly of an O-rin'gdisposed between the bore andthe piston. whereupon pressure fluid can pass through the device .torelieve the ressure. In this known device an annular gap of constantimensions is formed inwardly beyond the O-ring. The backor jreactionpressure produced in the. gapdeflnesthe maximum rate of flow of pressurefluid when the device operates. In the case of excessive pressure, duefor example to a rock fall i'n a mineral mine, the excessive pressurecannot be reduced quickly enough by. the device and consequently damageoccurs. I v v An object of this invention is to provide an improveddevice which will overcome this disadvantage.

A further object of theinvention is tomodify the known device as littleas possible to achieve this result.

SUMMARYOF Tm: INVENTION In the known pressure relief device of theaforementioned kind which has a pressure member transmitting the springforce to the piston the invention provides-that the longitudinal boreextends completely through thepiston and is closed at its innermost endby the pressure member under normal conditions.

With a device made in accordance with the invention two valves areeffectively provided in cascade. The second valve is a safety valvewhich only responds at excessive pressures greater than that at whichthe first valve responds. Generally speaking, the working area of thesecond, valve formed by the closure of thelongitudinal boreissmallerthan the working areas of the piston outer face. Thus, only ifexcessive pressure occurs are the piston and the pressure memberseparated to provide an increased rate of throughflow for the pressuremedium. 7 i

In order that the pressure member shall not load the piston nonuniformlya spherical or conical sealing means is preferably formed between thepressure member and the piston. The nature of the sealingmeansis-immaterial; for example a steel-synthetic plastics joint or evena steel on steel joint can be used;

To' ensure that the piston and pressure member reliably separate atexcessive pressure the stroke of the piston can be limited by theprovision of intenengageable abutment faces on 'the piston and the wallof the bore in the housing.

BRIEF DESCRIPTION or DRAWING DESCRIPTION or PREFERRED EMBODIMENTS In'the embodiment shown in FIG. 1 ahousing or body 5, which may be made intwo parts-as showmhas a cylindrical bore 2 which receives a valve pistonl for 'slidable displacement therein. The piston 1 has a longitudinalbore 3 which I communicates with a number of radial bores 4 terminatingat the peripheral surface of the piston l. The wall of the bore 2 isprovided with groove in which O-rings 6, 16 are sealed. The O-rings 16is positioned near the outermost working face of the piston l and theO-rings 6 is positioned inwardly therefrom. I

The body contains a chamber 7 having a defining radial surface 12adjoining the innermost end of the bore 2.

This innermost end of ,the bore 2 is tapered to increase in diameterover a portion 17. The body 5 has an outlet 18 communicating with thechamber 7..Axpressure member is I disposed in the chamber 7 andtransmits the force of a compression spring 1 l to the piston l. g TheO-ring 6 permits pressure fluid to pass from the working face of thepiston 1 to thecharnber 7 and the outlet 18 via the bores 3, 4 when thepressure acting-on the working face of the piston l is sufficiently highto overcome the force of the spring 11 and raise the piston 1 until thebores 4 are disposed above the 0 ring 6.

The operation of the device described so far is known per se. a i

In accordance with the invention the bore 3communicates with a chamber 8which is normally closed off from the chamber 7 by sealing means 9. Thecompression spring 1 1 acting on the pressure member 10 serves tomaintain the chamber 8 sealed relative to the chamber 7 during normalconditions and defines the setting of the device. The effective workingarea of the chamber 8 'is smaller than the working area of the piston 1so that the sealing means 9 will separate from the chamber 8 to permitfluid to enter the chamber 7 directly through the bore Jonly when thechamber 8 is subjected to pressure fluid at a pressure substantiallyhigher than that necessary to displace the piston 1. Thus, the valveconstituted inter alia by the chamber 8 only opens when the pressurerises decisively to a dangerous level.

In FIG. 2 like reference numerals denote like parts to those shown inFIG. 1. In contrast to FIG. 1 the innermost end of the piston 1 istapered to reduce in diameter and fonn a frustoconical portion 14. Abore 13 is provided in the pressure member 10 and the lower part of thisbore-13 forms a seating in which the portion 14 of the piston l isreceived. The opera tion of the device shown in FIG. 2 is the same asthat of the device shown in FIG. 1.

Again in FIG. 3 like reference numerals denote like parts to those shownin FIGS. 1 and 2. Apartfrom some relatively minor differences inconstruction the device of FIG. 3 has its piston 1 provided with astepped abutment face 15 engageable with a corresponding abutment face16 on the wall of the bore 2. In this way the stroke of the piston 2 islimited. When the pressure of the fluid reaches a certain value thepiston l and a sealing surface 9' for the bore 3 are raised. Excessivepressure will however separate the surface 9' from the bore 3 to permita more rapid through flow of fluid.

In each embodiment the invention provides with an advantageousmodification of the known device a device able to provide a largethrough flow passage in case of need.

We, claim: v 1. In a hydraulic pressure relief device with a housingpro- 1 vided with a bore, a piston mounted for sliding in the bore thepiston having a longitudinal bore extending inwardly of an outletworking face of the piston and communicating with one or more radialbores, an O-ring positioned between the piston and the bore and disposedinwardly of the working face of the piston a pressure member disposed inthe housing and a spring urging said pressure member into engagementwith the piston, the improvement comprising the longitudinal boreextends completely through the piston and sealing means between thepressure member and the piston servingto closethe innermost end of thebore under normal conditions.

. 2. A device according to claim 1 wherein the effective working area ofthe closure of the longitudinal bore by said sealing means is smallerthan theworking area of the piston.

bore in the housing;

d. a longitudinal axial bore extending through the piston andcommunicating with one or more radial bores disposed inwardly of theworking face of the piston;

e. a pressure member disposed in the chamber of the housing; and

f. a spring urging the pressure member against the piston so as to closethe innermost end of the longitudinal bore therein.

